Congress-led UDF took early lead in 13 of the 20 seats as officials counted the millions of votes polled in the Lok Sabha election.
The LDF led by the CPI-M was ahead in seven seats, officials said.
LDF candidates were forging ahead in Kannur, Vadakara, Attingal, Alalthur, Mavelikera, Thrissur and Chalakudy constituencies, and the UDF in Thiruvananthapuram, Alappuzha, Kottayam, Kasargode, Kozhikode, Ponnani, Ernakulam, Malappuram, Palakad, Idukki, Kollam, Idukki and Pathanamthitta.
In 2009, the UDF won 16 and the LDF four Lok Sabha seats.
The ruling Congress-led UDF is leading in eight seats and the LDF in two seats as the counting is progressing in all the 20 seats.
The leading Congress candidates include K V Thomas (Ernakulam), M I Shanawas (Wayanad), T Siddique (Kasargode) and M K Raghavan in Kozhikode are leading.
IUML candidates E Ahamed in Malappuram and E T Muhammad Basheer in Ponnani are also ahead of their LDF opponents.